Fuels compositions for direct injection gasoline engines containing manganese compounds

ABSTRACT

Deposits and soot formation in a direct injection gasoline engine are reduced by providing as fuel for the operation of said direct injection engine a fuel composition comprising a fuel-soluble cyclopentadienyl manganese tricarbonyl compound.

FIELD OF THE INVENTION

The present invention relates to new spark-ignition fuel compositionsand methods for controlling, i.e. reducing or eliminating, deposits andreducing soot formation in direct injection gasoline (DIG) engines. Moreparticularly, the invention relates to fuel compositions comprising aspark-ignition fuel and a manganese compound and the use of said fuelcompositions in DIG engines.

BACKGROUND OF THE INVENTION

Over the years considerable work has been devoted to additives forcontrolling (preventing or reducing) deposit formation in the fuelinduction systems of spark-ignition internal combustion engines. Inparticular, additives that can effectively control fuel injectordeposits, intake valve deposits and combustion chamber depositsrepresent the focal point of considerable research activities in thefield and despite these efforts, further improvements are desired.

Direct injection gasoline (DIG) technology is currently on a steepdevelopmental curve because of its high potential for improved fueleconomy and power. Environmentally, the fuel economy benefits translatedirectly into lower carbon dioxide emissions, a greenhouse gas that iscontributing to global warming.

Conventional multi-port injection (MPI) engines form a homogeneouspre-mixture of gasoline and air by injecting gasoline into the intakeport, while a direct injection gasoline engine injects gasoline directlyinto the combustion chamber like a diesel engine so that it becomespossible to form a stratified fuel mixture which is rich in theneighborhood of the spark plug but highly lean in the entire combustionchamber. Due to the formation of such a stratified fuel mixture,combustion with the overall highly lean mixture can be achieved, leadingto an improvement in fuel consumption approaching that of a dieselengine.

However, direct injection gasoline engines can encounter problemsdifferent from those of the conventional engines due to the directinjection of gasoline into the combustion chamber. One of these problemsis related to the smoke exhausted mainly from the part of the mixture inwhich the gasoline is excessively rich, upon the stratified combustion.The amount of soot produced is greater than that of a conventional MPIengine, thus a greater amount of soot can enter the lubricating oilthrough combustion gas blow by.

There are a number of technical issues to be resolved with DIGtechnology, and one of them is injector performance with differentgasoline fuels on the world market. Being located in the combustionchamber, DIG injectors are exposed to a much harsher environment thanconventional engines with port fuel injectors (PFI). This more severeenvironment can accelerate fuel degradation and oxidation to formdeposits.

DIG technology promises about a third less carbon dioxide emissions thancomparable conventional multi-port injection. This is achieved with a10-15% improvement in fuel consumption when operating in the homogeneousmode, and up to 35% when operating in the lean stratified mode. Fueleconomy benefits also translate into fossil energy conservation andsavings for the consumer. In addition, the DIG operation platformfacilitates up to a 10% power increase for the same fuel burned in theequivalent MPI configuration.

Current generation DIG technologies have experienced deposit problems.Areas of concern are fuel rails, injectors, combustion chamber (CCD),crankcase soot loadings, and intake valves (IVD). Deposits in the intakemanifold come in through the PCV valve and exhaust gas recirculation(EGR). Since there is no liquid fuel wetting the back of the intakevalves, these deposits build up quite quickly.

Injector deposits in DIG engines restrict fuel flow and alter spraycharacteristics of the injectors. Low levels of fuel flow restrictioncan be compensated for by engine control electronics. However, highlevels of flow restriction and any level of spray distortion cannot beadequately controlled electronically. In PFI engines, the cut-off point,as defined by the U.S. Environmental Protection Agency, for injectorflow restriction is 5% for any one injector when tested in accordancewith ASTM D 5598-94. This is because spray distortion is not much of anissue. In DIG engines, on the other hand, charge flow characteristics inthe cylinder are critical to the calibrations that go into driveability,fuel economy, and emissions. In-cylinder charge motion in DIG engines isvery sensitive to injector spray distortion. For this reason, DIGinjector flow restriction cut-off point may be much lower than the 5%level assigned to PFI injector performance.

Fuel related deposits in direct injection gasoline (DIG) engines are anissue of current interest since this technology is now commercial inJapan and Europe. Fuel injector performance is at the forefront of thisissue because the DIG combustion system relies heavily on fuel sprayconsistency to realize its advantages in fuel economy and power, and tominimize exhaust emissions. A consistent spray pattern enables moreprecise electronic control of the combustion event and the exhaustafter-treatment system.

There are numerous references teaching fuel compositions containingmanganese compounds, for example, U.S. Pat. Nos. 5,551,957; 5,679,116;and 5,944,858. However, none of these references teach the use of fuelcompositions containing manganese compounds in direct injection gasolineengines or the impact manganese compounds have on deposits in theseengines.

SUMMARY OF THE INVENTION

The present invention is directed to a fuel composition comprising (a) aspark-ignition internal combustion fuel; and (b) a cyclopentadienylmanganese tricarbonyl compound. Further, this invention is directed tomethods of controlling deposits and reducing soot formation in directinjection gasoline engines.

DETAILED DESCRIPTION OF THE INVENTION

Cyclopentadienyl Manganese Tricarbonyl Compounds

Cyclopentadienyl manganese tricarbonyl compounds which can be used inthe practice of this invention include cyclopentadienyl manganesetricarbonyl, methylcyclopentadienyl manganese tricarbonyl,dimethylcyclopentadienyl manganese tricarbonyl,trimethylcyclopentadienyl manganese tricarbonyl,tetramethylcyclopentadienyl manganese tricarbonyl,pentamethylcyclopentadienyl manganese tricarbonyl, ethylcyclopentadienylmanganese tricarbonyl, diethylcyclopentadienyl manganese tricarbonyl,propylcyclopentadienyl manganese tricarbonyl, isopropylcyclopentadienylmanganese tricarbonyl, tert-butylcyclopentadienyl manganese tricarbonyl,octylcyclopentadienyl manganese tricarbonyl, dodecylcyclopentadienylmanganese tricarbonyl, ethylmethylcyclopentadienyl manganesetricarbonyl, indenyl manganese tricarbonyl, and the like, includingmixtures of two or more such compounds. Preferred are thecyclopentadienyl manganese tricarbonyls which are liquid at roomtemperature such as methylcyclopentadienylmanganesetricarbonyl,ethylcyclopentadienyl manganese tricarbonyl, liquid mixtures ofcyclopentadienyl manganese tricarbonyl and methylcyclopentadienylmanganese tricarbonyl, mixtures of methylcyclopentadienyl manganesetricarbonyl and ethylcyclopentadienyl manganese tricarbonyl, etc.Preparation of such compounds is described in the literature, forexample, U.S. Pat. No. 2,818,417, the disclosure of which isincorporated herein in its entirety.

When formulating the fuel compositions of this invention, thecyclopentadienyl manganese tricarbonyl compounds are employed in amountssufficient to reduce or inhibit deposit and/or soot formation in adirect injection gasoline engine. Thus the fuels will contain minoramounts of the cyclopentadienyl manganese tricarbonyl compounds thatcontrol, eliminate or reduce, formation of engine deposits, especiallyinjector deposits and/or control soot formation. Generally speaking thefuels of the invention will contain an amount of the cyclopentadienylmanganese tricarbonyl compound sufficient to provide from about 0.0078to about 0.25 gram of manganese per gallon of fuel, and preferably fromabout 0.0156 to about 0.125 gram of manganese per gallon.

The fuel compositions of the present invention may contain supplementaladditives in addition to the manganese compounds described above. Saidsupplemental additives include dispersants/detergents, antioxidants,carrier fluids, metal deactivators, dyes, markers, corrosion inhibitors,biocides, antistatic additives, drag reducing agents, demulsifiers,dehazers, anti-icing additives, antiknock additives, anti-valve-seatrecession additives, lubricity additives and combustion improvers.

The fuel compositions of the present invention may, and typically do,contain amine detergents. Suitable amine detergents for use in thepresent invention include hydrocarbyl succinic anhydride derivatives,Mannich condensation products, hydrocarbyl amines and polyetheramines.When used, the amine detergents are typically present in an amount offrom 5 to 100 pounds by weight of additive per thousand barrels byvolume of fuel.

The hydrocarbyl-substituted succinic anhydride derivatives suitable foruse in the present invention include hydrocarbyl succinimides,succinamides, succinimide-amides and succinimide-esters. Thehydrocarbyl-substituted succinic anhydride derivatives are typicallyprepared by reacting a hydrocarbyl-substituted succinic acylating agentwith a polyamine.

The hydrocarbyl-substituted succinic acylating agents include thehydrocarbyl-substituted succinic acids, the hydrocarbyl-substitutedsuccinic anhydrides, the hydrocarbyl-substituted succinic acid halides(especially the acid fluorides and acid chlorides), and the esters ofthe hydrocarbyl-substituted succinic acids and lower alcohols (e.g.,those containing up to 7 carbon atoms), that is, hydrocarbyl-substitutedcompounds which can function as carboxylic acylating agents. Of thesecompounds, the hydrocarbyl-substituted succinic acids and thehydrocarbyl-substituted succinic anhydrides and mixtures of such acidsand anhydrides are generally preferred, the hydrocarbyl-substitutedsuccinic anhydrides being particularly preferred.

The acylating agent for producing the detergent is preferably made byreacting a polyolefin of appropriate molecular weight (with or withoutchlorine) with maleic anhydride. However, similar carboxylic reactantscan be employed such as maleic acid, fumaric acid, malic acid, tartaricacid, itaconic acid, itaconic anhydride, citraconic acid, citraconicanhydride, mesaconic acid, ethylmaleic anhydride, dimethylmaleicanhydride, ethylmaleic acid, dimethylmaleic acid, hexylmaleic acid, andthe like, including the corresponding acid halides and lower aliphaticesters.

For example, hydrocarbyl-substituted succinic anhydrides may be preparedby the thermal reaction of a polyolefin and maleic anhydride, asdescribed, for example in U.S. Pat. Nos. 3,361,673 and 3,676,089.Alternatively, the substituted succinic anhydrides can be prepared bythe react on of chlorinated polyolefins with maleic anhydride, asdescribed, for example, in U.S. Pat. No. 3,172,892. A further discussionof hydrocarbyl-substituted succinic anhydrides can be found, forexample, in U.S. Pat. Nos. 4,234,435; 5,620,486 and 5,393,309.

The mole ratio of maleic anhydride to olefin can vary widely. It mayvary, for example, from 5:1 to 1:5, a more preferred range is 3:1 to1:3, preferably the maleic anhydride is used in stoichiometric excess,e.g. 1.1-5 moles maleic anhydride per mole of olefin. The unreactedmaleic anhydride can be vaporized from the resultant reaction mixture.

Polyalkenyl succinic anhydrides may be converted to polyalkyl succinicanhydrides by using conventional reducing conditions such as catalytichydrogenation. For catalytic hydrogenation, a preferred catalyst ispalladium on carbon. Likewise, polyalkenyl succinimides may be convertedto polyalkyl succinimides using similar reducing conditions.

The hydrocarbyl substituent on the succinic anhydrides employed in theinvention is generally derived from polyolefins that are polymers orcopolymers of mono-olefins, particularly 1-mono-olefins, such asethylene, propylene, butylene, and the like. Preferably, the mono-olefinemployed will have 2 to about 24 carbon atoms, and more preferably,about 3 to 12 carbon atoms. More preferred mono-olefins includepropylene, butylene, particularly isobutylene, 1-octene and 1-decene.Polyolefins prepared from such mono-olefins include polypropylene,polybutene, polyisobutene, and the polyalphaolefins produced from1-octene and 1-decene.

A particularly preferred polyalkyl or polyalkenyl substituent is onederived from polyisobutene. Suitable polyisobutenes for use in preparingthe succinimide-acids of the present invention include thosepolyisobutenes that comprise at least about 20% of the more reactivemethylvinylidene isomer, preferably at least 50% and more preferably atleast 70%. Suitable polyisobutenes include those prepared using BF₃catalysts. The preparation of such polyisobutenes in which themethylvinylidene isomer comprises a high percentage of the totalcomposition is described in U.S. Pat. Nos. 4,152,499 and 4,605,808.

Hydrocarbyl succinimides are obtained by reacting ahydrocarbyl-substitued succinic anhydride, acid, acid-ester or loweralkyl ester with an amine containing at least one primary amine group.Representative examples are given in U.S. Pat. Nos. 3,172,892;3,202,678; 3,219,666; 3,272,746; 3,254,025, 3,216,936, 4,234,435; and5,575,823. The alkenyl succinic anhydride may be prepared readily byheating a mixture of olefin and maleic anhydride to about 180-220° C.The olefin is preferably a polymer or copolymer of a lower monoolefinsuch as ethylene, propylene, isobutene and the like. The more preferredsource of alkenyl group is from polyisobutene having a molecular weightup to 5000 or higher. In a still more, preferred embodiment the alkenylis a polyisobutene group having a molecular weight of about 500-2000 andmost preferably about 700-1500.

Amines which may be reacted with the alkenyl succinic anhydride to formthe hydrocarbyl-succinimide include any that have at least one primaryamine group that can react to form an imide group. A few representativeexamples are: methylamine, 2-ethylhexylamine, n-dodecylamine,stearylamine, N,N-dimethyl-propanediamine, N-(3-aminopropyl)morpholine,N-dodecyl propanediamine, N-aminopropyl piperazine ethanolamine,N-ethanol ethylene diamine and the like. Preferred amines include thealkylene polyamines such as propylene diamine, dipropylene triamine,di-(1,2butylene)-triamine, tetra-(1,2-propylene)pentaamine.

The most preferred amines are the ethylene polyamines which have theformula H₂N(CH₂CH₂NH)_(n)H wherein n is an integer from one to ten.These ethylene polyamines include ethylene diamine, diethylene triamine,triethylene tetraamine, tetraethylene pentaamine, pentaethylenehexaamine, and the like, including mixtures thereof in which case n isthe average value of the mixture. These ethylene polyamines have aprimary amine group at each end so can form mono-alkenylsuccinimides andbis-alkenylsuccinimides. Thus especially preferred hydrocarbylsuccinimides for use in the present invention are the products ofreaction of a polyethylenepolyamine, e.g. triethylene tetramine ortetraethylene pentamine, with a hydrocarbon substituted carboxylic acidor anhydride made by reaction of a polyolefin, preferably polyisobutene,having a molecular weight of 500 to 2,000, especially 700 to 1500, withan unsaturated polycarboxylic acid or anhydride, e.g. maleic anhydride.

The Mannich base detergents of the present invention are the reactionproducts of an alkyl-substituted hydroxyaromatic compound, aldehydes andamines. The alkyl-substituted hydroxyaromatic compound, aldehydes andamines used in making the Mannich reaction products of the presentinvention may be any such compounds known and applied in the art, inaccordance with the foregoing limitations.

Representative alkyl-substituted hydroxyaromatic compounds that may beused in forming the present Mannich base products are polypropylphenol(formed by alkylating phenol with polypropylene), polybutylphenols(formed by alkylating phenol with polybutenes and/or polyisobutylene),and polybutyl-co-polypropylphenols (formed by alkylating phenol with acopolymer of butylene and/or butylene and propylene). Other similarlong-chain alkylphenols may also be used. Examples include phenolsalkylated with copolymers of butylene and/or isobutylene and/orpropylene, and one or more mono-olefinic comonomers copolymerizabletherewith (e.g., ethylene, 1-pentene, 1-hexene, 1-octene, 1-decene,etc.) where the copolymer molecule contains at least 50% by weight, ofbutylene and/or isobutylene and/or propylene units. The comonomerspolymerized with propylene or such butenes may be aliphatic and can alsocontain non-aliphatic groups, e.g., styrene, o-methylstyrene,p-methylstyrene, divinyl benzene and the like. Thus in any case theresulting polymers and copolymers used in forming the alkyl-substitutedhydroxyaromatic compounds are substantially aliphatic hydrocarbonpolymers.

Polybutylphenol (formed by alkylating phenol with polybutylene) ispreferred. Unless otherwise specified herein, the term “polybutylene” isused in a generic sense to include polymers made from “pure” or“substantially pure” 1-butene or isobutene, and polymers made frommixtures of two or all three of 1-butene, 2-butene and isobutene.Commercial grades of such polymers may also contain insignificantamounts of other olefins. So-called high reactivity polyisobuteneshaving relatively high proportions of polymer molecules having aterminal vinylidene group are also suitable for use in forming the longchain alkylated phenol reactant. Suitable high-reactivity polyisobutenesinclude those polyisobutenes that comprise at least about 20% of themore reactive methylvinylidene isomer, preferably at least 50% and morepreferably at least 70%. Suitable polyisobutenes include those preparedusing BF₃ catalysts. The preparation of such polyisobutenes in which themethylvinylidene isomer comprises a high percentage of the totalcomposition is described in U.S. Pat. Nos. 4,152,499 and 4,605,808.

The alkylation of the hydroxyaromatic compound is typically performed inthe presence of an alkylating catalyst at a temperature in the range ofabout 0 to about 200° C., preferably 0 to 100° C. Acidic catalysts aregenerally used to promote Friedel-Crafts alkylation. Typical catalystsused in commercial production include sulphuric acid, BF₃, aluminumphenoxide, methanesulphonic acid, cationic exchange resin, acidic claysand modified zeolites.

The long chain alkyl substituents on the benzene ring of the phenoliccompound are derived from polyolefin having a number average molecularweight (M_(n)) of from about 500 to about 3000, preferably from about500 to about 2100, as determined by gel permeation chromatography (GPC).It is also preferred that the polyolefin used have a polydispersity(weight average molecular weight/number average molecular weight) in therange of about 1 to about 4 (preferably from about 1 to about 2) asdetermined by GPC.

The Mannich detergent may be made from a long chain alkylphenol.However, other phenolic compounds may be used including high molecularweight alkyl-substituted derivatives of cresol, resorcinol,hydroquinone, catechol, hydroxydiphenyl, benzylphenol, phenethylphenol,naphthol, tolylnaphthol, among others. Preferred for the preparation ofthe Mannich detergents are the polyalkylphenol and polyalkylcresolreactants, e.g., polypropylphenol, polybutylphenol, polypropylcresol andpolybutylcresol, wherein the alkyl group has a number average molecularweight of about 500 to about 2100, while the most preferred alkyl groupis a polybutyl group derived from polyisobutylene having a numberaverage molecular weight in the range of about 800 to about 1300.

The preferred configuration of the alkyl-substituted hydroxyaromaticcompound is that of a para-substituted mono-alkylphenol or apara-substituted mono-alkyl ortho-cresol. However, any alkylphenolreadily reactive in the Mannich condensation reaction may be employed.Thus, Mannich products made from alkylphenols having only one ring alkylsubstituent, or two or more ring alkyl substituents are suitable for usein this invention. The long chain alkyl substituents may contain someresidual unsaturation, but in general, are substantially saturated alkylgroups.

Representative amine reactants include, but are not limited to, alkylenepolyamines having at least one suitably reactive primary or secondaryamino group in the molecule. Other substituents such as hydroxyl, cyano,amido, etc., can be present in the polyamine. In a preferred embodiment,the alkylene polyamine is a polyethylene polyamine. Suitable alkylenepolyamine reactants include ethylenediamine, diethylenetriamine,triethylenetetramine, tetraethylenepentamine and mixtures of such amineshaving nitrogen contents corresponding to alkylene polyamines of theformula H₂N-(A-NH—)_(n)H, where A is divalent ethylene or propylene andn is an integer of from 1 to 10, preferably 1 to 4. The alkylenepolyamines may be obtained by the reaction of ammonia and dihaloalkanes, such as dichloro alkanes.

In another preferred embodiment of the present invention, the amine isan aliphatic diamine having one primary or secondary amino group and atleast one tertiary amino group in the molecule. Examples of suitablepolyamines include N,N,N″,N″-tetraalkyldialkylenetriamines (two terminaltertiary amino groups and one central secondary amino group),N,N,N′,N″-tetraalkyltrialkylenetetramines (one terminal tertiary aminogroup, two internal tertiary amino groups and one terminal primary aminogroup), N,N,N′,N″,N′″-pentaalkyltrialkylenetetramines (one terminaltertiary amino group, two internal tertiary amino groups and oneterminal secondary amino group), N,N-dihydroxyalkyl-alpha,omega-alkylenediamines (one terminal tertiary amino group and oneterminal primary amino group), N,N,N′-trihydroxyalkyl-alpha,omega-alkylenediamines (one terminal tertiary amino group and oneterminal secondary amino group),tris(dialkylaminoalkyl)aminoalkylmethanes (three terminal tertiary aminogroups and one terminal primary amino group), and similar compounds,wherein the alkyl groups are the same or different and typically containno more than about 12 carbon atoms each, and which preferably containfrom 1 to 4 carbon atoms each. Most preferably these alkyl groups aremethyl and/or ethyl groups. Preferred polyamine reactants areN,N-dialkyl-alpha, omega-alkylenediamine, such as those having from 3 toabout 6 carbon atoms in the alkylene group and from 1 to about 12 carbonatoms in each of the alkyl groups, which most preferably are the samebut which can be different. Most preferred isN,N-dimethyl-1,3-propanediamine and N-methyl piperazine.

Examples of polyamines having one reactive primary or secondary aminogroup that can participate in the Mannich condensation reaction, and atleast one sterically hindered amino group that cannot participatedirectly in the Mannich condensation reaction to any appreciable extentinclude N-(tert-butyl)-1,3-propanediamine,N-neopentyl-1,3-propanediamine,N-(tert-butyl)-1-methyl-1,2-ethanediamine,N-(tert-butyl)-1-methyl-1,3-propanediamine, and3,5-di(tert-butyl)aminoethylpiperazine.

Representative aldehydes for use in the preparation of the Mannich baseproducts include the aliphatic aldehydes such as formaldehyde,acetaldehyde, propionaldehyde, butyraldehyde, valeraldehyde,caproaldehyde, heptaldehyde, stearaldehyde. Aromatic aldehydes which maybe used include benzaldehyde and salicylaldehyde. Illustrativeheterocyclic aldehydes for use herein are furfural and thiophenealdehyde, etc. Also useful are formaldehyde-producing reagents such asparaformaldehyde, or aqueous formaldehyde solutions such as formalin.Most preferred is formaldehyde or formalin.

The condensation reaction among the alkylphenol, the specified amine(s)and the aldehyde may be conducted at a temperature typically in therange of about 40° to about 200° C. The reaction can be conducted inbulk (no diluent or solvent) or in a solvent or diluent. Water isevolved and can be removed by azeotropic distillation during the courseof the reaction. Typically, the Mannich reaction products are formed byreacting the alkyl-substituted hydroxyaromatic compound, the amine andaldehyde in the molar ratio of 1.0:0.5-2.0:1.0-3.0, respectively.

Suitable Mannich base detergents for use in the present inventioninclude those detergents taught in U.S. Pat. Nos. 4,231,759; 5,514,190;5,634,951; 5,697,988; 5,725,612; and 5,876,468, the disclosures of whichare incorporated herein by reference.

Hydrocarbyl amine detergents are known materials prepared by knownprocess technology. One common process involves halogenation of a longchain aliphatic hydrocarbon such as a polymer of ethylene, propylene,butylene, isobutene, or copolymers such as ethylene and propylene,butylene and isobutylene, and the like, followed by reaction of theresultant halogenated hydrocarbon with a polyamine. If desired, at leastsome of the product can be converted into an amine salt by treatmentwith an appropriate quantity of an acid. The products formed by thehalogenation route often contain a small amount of residual halogen suchas chlorine. Another way of producing suitable aliphatic polyaminesinvolves controlled oxidation (e.g., with air or a peroxide) of apolyolefin such as polyisobutene followed by reaction of the oxidizedpolyolefin with a polyamine. For synthesis details for preparing suchaliphatic polyamine detergent/dispersants, see for example U.S. Pat.Nos. 3,438,757; 3,454,555; 3,485,601; 3,565,804; 3,573,010; 3,574,576;3,671,511; 3,746,520; 3,756,793; 3,844,958; 3,852,258; 3,864,098;3,876,704; 3,884,647; 3,898,056; 3,950,426; 3,960,515; 4,022,589;4,039,300; 4,128,403; 4,166,726; 4,168,242; 5,034,471; 5,086,115;5,112,364; and 5,124,484; and published European Patent Application384,086. The disclosures of each of the foregoing documents areincorporated herein by reference. The long chain substituent(s) of thehydrocarbyl amine detergent most preferably contain(s) an average of 50to 350 carbon atoms in the form of alkyl or alkenyl groups (with orwithout a small residual amount of halogen substitution). Alkenylsubstituents derived from poly-alpha-olefin homopolymers or copolymersof appropriate molecular weight (e.g., propene homopolymers, butenehomopolymers, C₃ and C₄ alpha-olefin copolymers, and the like) aresuitable. Most preferably, the substituent is a polyisobutenyl groupformed from polyisobutene having a number average molecular weight (asdetermined by gel permeation chromatography) in the range of 500 to2000, preferably 600 to 1800, most preferably 700 to 1600.

Polyetheramines suitable for use as the detergents of the presentinvention are “single molecule” additives, incorporating both amine andpolyether functionalities within the same molecule. The polyetherbackbone can be based on propylene oxide, ethylene oxide, butyleneoxide, or mixtures of these. The most preferred are propylene oxide orbutylene oxide or mixture thereof to impart good fuel solubility. Thepolyetheramines can be monoamines, diamines or triamines. Examples ofcommercially available polyetheramines are those under the tradenameJeffamines™ available from Huntsman Chemical company. The molecularweight of the polyetheramines will typically range from 500 to 3000.Other suitable polyetheramines are those compounds taught in U.S. Pat.Nos. 4,288,612; 5,089,029; and 5,112,364.

When formulating the fuel compositions of this invention, the manganesecompound (with our without other additives) is employed in amountssufficient to reduce or eliminate deposits including injector depositsand/or control soot formation. Thus the fuels will contain minor amountsof the manganese compound proportioned so as to prevent or reduceformation of engine deposits, especially fuel injector deposits.Generally speaking the fuel compositions of this invention will containan amount of manganese compound sufficient to provide from about 0.0078to about 0.25 gram of manganese per gallon of fuel, and preferably fromabout 0.0156 to about 0.125 gram of manganese per gallon.

The base fuels used in formulating the fuel compositions of the presentinvention include any base fuels suitable for use in the operation ofdirect injection gasoline engines such as leaded or unleaded motorgasolines, and so-called reformulated gasolines which typically containboth hydrocarbons of the gasoline boiling range and fuel-solubleoxygenated blending agents (“oxygenates”), such as alcohols, ethers andother suitable oxygen-containing organic compounds. Preferably, the fuelis a mixture of hydrocarbons boiling in the gasoline boiling range. Thisfuel may consist of straight chain or branch chain paraffins,cycloparaffins, olefins, aromatic hydrocarbons or any mixture of these.The gasoline can be derived from straight run naptha, polymer gasoline,natural gasoline or from catalytically reformed stocks boiling in therange from about 80° to about 450° F. The octane level of the gasolineis not critical and any conventional gasoline may be employed in thepractice of this invention.

Oxygenates suitable for use in the present invention include methanol,ethanol, isopropanol, t-butanol, mixed C1 to C5 alcohols, methyltertiary butyl ether, tertiary amyl methyl ether, ethyl tertiary butylether and mixed ethers. Oxygenates, when used, will normally be presentin the base fuel in an amount below about 30% by volume, and preferablyin an amount that provides an oxygen content in the overall fuel in therange of about 0.5 to about 5 percent by volume.

In a preferred embodiment, the detergents are preferably used with aliquid carrier or induction aid. Such carriers can be of various types,such as for example liquid poly-α-olefin oligomers, mineral oils, liquidpoly(oxyalkylene) compounds, liquid alcohols or polyols, polyalkenes,liquid esters, and similar liquid carriers. Mixtures of two or more suchcarriers can be employed.

Preferred liquid carriers include 1) a mineral oil or a blend of mineraloils that have a viscosity index of less than about 120, 2) one or morepoly-α-olefin oligomers, 3) one or more poly(oxyalkylene) compoundshaving an average molecular weight in the range of about 500 to about3000, 4) polyalkenes, 5) polyalkyl-substituted hydroxyaromatic compoundsor 6) mixtures thereof. The mineral oil carrier fluids that can be usedinclude paraffinic, naphthenic and asphaltic oils, and can be derivedfrom various petroleum crude oils and processed in any suitable manner.For example, the mineral oils may be solvent extracted or hydrotreatedoils. Reclaimed mineral oils can also be used. Hydrotreated oils are themost preferred. Preferably the mineral oil used has a viscosity at 40°C. of less than about 1600 SUS, and more preferably between about 300and 1500 SUS at 40° C. Paraffinic mineral oils most preferably haveviscosities at 40° C. in the range of about 475 SUS to about 700 SUS.For best results, it is highly desirable that the mineral oil have aviscosity index of less than about 100, more preferably, less than about70 and most preferably in the range of from about 30 to about 60.

The poly-α-olefins (PAO) suitable for use as carrier fluids are thehydrotreated and unhydrotreated poly-α-olefin oligomers, i.e.,hydrogenated or unhydrogenated products, primarily trimers, tetramersand pentamers of α-olefin monomers, which monomers contain from 6 to 12,generally 8 to 12 and most preferably about 10 carbon atoms. Theirsynthesis is outlined in Hydrocarbon Processing, February 1982, page 75et seq., and in U.S. Pat. Nos. 3,763,244; 3,780,128; 4,172,855;4,218,330; and 4,950,822. The usual process essentially comprisescatalytic oligomerization of short chain linear alpha olefins (suitablyobtained by catalytic treatment of ethylene). The poly-α-olefins used ascarriers will usually have a viscosity (measured at 100° C.) in therange of 2 to 20 centistokes (cSt). Preferably, the poly-α-olefin has aviscosity of at least 8 cSt, and most preferably about 10 cSt at 100° C.

The poly (oxyalkylene) compounds which are among the preferred carrierfluids for use in this invention are fuel-soluble compounds which can berepresented by the following formulaR₁—(R₂—O)_(n)—R₃wherein R₁ is typically a hydrogen, alkoxy, cycloalkoxy, hydroxy, amino,hydrocarbyl (e.g., alkyl, cycloalkyl, aryl, alkylaryl, aralkyl, etc.),amino-substituted hydrocarbyl, or hydroxy-substituted hydrocarbyl group,R₂ is an alkylene group having 2-10 carbon atoms (preferably 2-4 carbonatoms), R₃ is typically a hydrogen, alkoxy, cycloalkoxy, hydroxy, amino,hydrocarbyl (e.g., alkyl, cycloalkyl, aryl, alkylaryl, aralkyl, etc.),amino-substituted hydrocarbyl, or hydroxy-substituted hydrocarbyl group,and n is an integer from 1 to 500 and preferably in the range of from 3to 120 representing the number (usually an average number) of repeatingalkyleneoxy groups. In compounds having multiple —R₂—O— groups, R₂ canbe the same or different alkylene group and where different, can bearranged randomly or in blocks. Preferred poly (oxyalkylene) compoundsare monools comprised of repeating units formed by reacting an alcoholwith one or more alkylene oxides, preferably one alkylene oxide, morepreferably propylene oxide or butylene oxide.

The average molecular weight of the poly (oxyalkylene) compounds used ascarrier fluids is preferably in the range of from about 500 to about3000, more preferably from about 750 to about 2500, and most preferablyfrom above about 1000 to about 2000.

One useful sub-group of poly (oxyalkylene) compounds is comprised of thehydrocarbyl-terminated poly(oxyalkylene) monools such as are referred toin the passage at column 6, line 20 to column 7 line 14 of U.S. Pat. No.4,877,416 and references cited in that passage, said passage and saidreferences being fully incorporated herein by reference.

A preferred sub-group of poly (oxyalkylene) compounds is comprised ofone or a mixture of alkylpoly (oxyalkylene)monools which in itsundiluted state is a gasoline-soluble liquid having a viscosity of atleast about 70 centistokes (cSt) at 40° C. and at least about 13 cSt at100° C. Of these compounds, monools formed by propoxylation of one or amixture of alkanols having at least about 8 carbon atoms, and morepreferably in the range of about 10 to about 18 carbon atoms, areparticularly preferred.

The poly (oxyalkylene) carriers used in the practice of this inventionpreferably have viscosities in their undiluted state of at least about60 cSt at 40° C. (more preferably at least about 70 cSt at 40° C.) andat least about 11 cSt at 100° C. (more preferably at least about 13 cStat 100° C.). In addition, the poly (oxyalkylene) compounds used in thepractice of this invention preferably have viscosities in theirundiluted state of no more than about 400 cSt at 40° C. and no more thanabout 50 cSt at 100° C. More preferably, their viscosities will notexceed about 300 cSt at 40° C. and will not exceed about 40 cSt at 100°C.

Preferred poly (oxyalkylene) compounds also include poly (oxyalkylene)glycol compounds and monoether derivatives thereof that satisfy theabove viscosity requirements and that are comprised of repeating unitsformed by reacting an alcohol or polyalcohol with an alkylene oxide,such as propylene oxide and/or butylene oxide with or without use ofethylene oxide, and especially products in which at least 80 mole % ofthe oxyalkylene groups in the molecule are derived from 1,2-propyleneoxide. Details concerning preparation of such poly(oxyalkylene)compounds are referred to, for example, in Kirk-Othmer, Encyclopedia ofChemical Technology, Third Edition, Volume 18, pages 633-645 (Copyright1982 by John Wiley & Sons), and in references cited therein, theforegoing excerpt of the Kirk-Othmer encyclopedia and the referencescited therein being incorporated herein in toto by reference. U.S. Pat.Nos. 2,425,755; 2,425,845; 2,448,664; and 2,457,139 also describe suchprocedures, and are fully incorporated herein by reference.

The poly (oxyalkylene) compounds, when used, pursuant to this inventionwill contain a sufficient number of branched oxyalkylene units (e.g.,methyldimethyleneoxy units and/or ethyldimethyleneoxy units) to renderthe poly (oxyalkylene) compound gasoline soluble.

Suitable poly (oxyalkylene) compounds for use in the present inventioninclude those taught in U.S. Pat. Nos. 5,514,190; 5,634,951; 5,697,988;5,725,612; 5,814,111 and 5,873,917, the disclosures of which areincorporated herein by reference.

The polyalkenes suitable for use as carrier fluids in the presentinvention include polypropene and polybutene. The polyalkenes of thepresent invention preferably have a molecular weight distribution(Mw/Mn) of less than 4. In a preferred embodiment, the polyalkenes havea MWD of 1.4 or below. Preferred polybutenes have a number averagemolecular weight (Mn) of from about 500 to about 2000, preferably 600 toabout 1000, as determined by gel permeation chromatography (GPC).Suitable polyalkenes for use in the present invention are taught inco-pending U.S. application Ser. No. 09/201,113 filed Nov. 30, 1998.

The polyalkyl-substituted hydroxyaromatic compounds suitable for use ascarrier fluid in the present invention include those compounds known inthe art as taught in U.S. Pat. Nos. 3,849,085; 4,231,759; 4,238,628;5,300,701; 5,755,835 and 5,873,917, the disclosures of which areincorporated herein by reference.

When the carrier fluids are used in combination with the aminedetergents, the ratio (wt/wt) of detergent to carrier fluid(s) istypically in the range of from 1:0.1 to 1:3.

The additives used in formulating the preferred fuels of the presentinvention can be blended into the base fuel individually or in varioussub-combinations. However, it is preferable to blend all of thecomponents concurrently using an additive concentrate as this takesadvantage of the mutual compatibility afforded by the combination ofingredients when in the form of an additive concentrate. Also use of aconcentrate reduces blending time and lessens the possibility ofblending errors.

A preferred embodiment of the present invention comprises a method forcontrolling injector deposits in a direct injection gasoline enginewhich comprises introducing into a direct injection gasoline engine withthe combustion intake charge a spark-ignition fuel compositioncomprising a) a spark-ignition fuel and b) a fuel-solublecyclopentadienyl manganese tricarbonyl compound.

Another preferred embodiment of the present invention comprises a methodfor reducing soot loading in the crankcase lubricating oil of a vehiclehaving a direct injection gasoline engine which comprises introducinginto a direct injection gasoline engine with the combustion intakecharge a spark-ignition fuel composition comprising a) a spark-ignitionfuel and b) a fuel-soluble cyclopentadienyl manganese tricarbonylcompound.

EXAMPLES

The practice and advantages of this invention are demonstrated by thefollowing examples which are presented for purposes of illustration andnot limitation.

The manganese compound used in the following examples wasmethylcyclopentadienyl manganese tricarbonyl (MMT).

The Mannich detergents used in the following examples were derived byreaction of a long chain alkylated phenol (“PBP”),N,N-dimethyl-1,3-propanediamine (“DMPD”), and formaldehyde (“FA”). ThePBP was formed by reacting phenol with a polyisobutylene having analkylvinylidene isomer content of less than 10% and a number averagemolecular weight of about 900.

To demonstrate the effectiveness of the additive systems of the presentinvention in reducing deposits in direct injection gasoline engines,tests were conducted in a 1982 Nissan Z22e (2.2 liter) dual-sparkplug,four-cylinder engine modified to run in a homogeneous direct injectionmode, at a fuel rich lambda of 0.8 to accelerate injector depositformation. Details of this test are set forth in Aradi, A. A., Imoehl,B., Avery, N. L., Wells, P. P., and Grosser, R. W.: “The Effect of FuelComposition and Engine Operating Parameters on Injector Deposits in aHigh-Pressure Direct Injection Gasoline (DIG) Research Engine”, SAETechnical Paper 1999-01-3690 (1999).

Modifications to the engine included replacing the exhaust-side sparkplugs with pre-production high-pressure common rail direct injectors,removing the OEM spark and fuel system, and installing a high-pressurefuel system and universal engine controller. Table 1 summarizes thespecifications of the modified test engine. For homogeneous combustion,flat-top pistons and the conventional gasoline spark ignition combustionchamber design were found to be sufficient for this type of researchwork. The injectors were located on the hot (i.e. exhaust) side of theengine to favor high tip temperatures to promote injector deposit.

The rate of injector deposit formation was evaluated through the use ofthis specially developed steady-state engine test. Engine operatingconditions for each test point were determined by mapping injector tiptemperatures throughout the engine operating map range. The injectorswere modified with thermocouples at the tip. Key parameters were inletair and fuel temperatures, engine speed, and engine load. The inlet airand fuel temperatures were subsequently controlled at 35° C. and 32° C.,respectively.

TABLE 1 Test Engine Specifications Four Cylinder In-Line 2.2 L NissanType Engine Converted for DI Operation Displacement 2187 cubiccentimeters Plugs/cylinder 1 (stock configuration: 2) Valves/cylinder 2Bore 87 millimeters Stroke 92 millimeters Fuel System Common Rail HighPressure Direct Injection Fuel Pressure 6900 kPa (closed loop) EngineController Universal Laboratory System Injection Timing 300 degrees BTDCCoolant Temperature (° C.) 85 Oil Temperature (° C.) 95

At constant inlet air/fuel temperature and engine load, tip temperatureremained constant at engine speeds of 1500, 2000, 2500, and 3000 rpm.However, at constant engine speed, tip temperatures increase with load.For five load points, 200, 300, 400, 500, and 600 mg/stroke air charge,increasing tip temperatures of 120, 140, 157, 173, and 184° C.,respectively, were observed for each load.

Through previous research, it was determined that a tip temperature of173° C. provided optimum conditions for injector deposit formation inthis engine. Table 2 sets forth the key test conditions used inperforming the evaluation of the additives of the present invention.

TABLE 2 Key Test Conditions Engine Speed (rpm) 2500 Inlet Air Temp. (°C.) 35 Inlet Fuel Temp. (° C.) 32 Exit Coolant Temp. (° C.) 85 Exit OilTemp. (° C.) 95 Load (mg air/stroke) 500 Injector Tip Temp. (° C.) 173

The test was divided into three periods: engine warm-up, anoperator-assisted period, and test period. Engine speed was controlledusing the engine dynamometer controller, and the engine throttle wasmanipulated to control air charge using a standard automotive airflowmeter as feedback in a closed-loop control system. Engine fueling wascontrolled in two ways. During warm-up, injector pulse width wascontrolled using a standard mass airflow strategy and exhaust gas sensorcontrolling the air/fuel mixture to stoichiometric. During the operatorinteraction period, the pulse width was manually set for each injectorusing wide-range lambda sensors in the exhaust port of each cylinder.Fuel flow was measured using a volumetric flow meter and atemperature-corrected density value was used to calculate mass flow.

Each fuel was run at a load condition of 500 mg/stroke. Injector depositformation was followed by measuring total engine fuel flow at fixedspeed, air charge (mass of air per intake stroke), and the lambda signalfrom each cylinder over a test period of six hours.

To help minimize injector-to-injector variability the same set ofinjectors was used for all tests at a particular engine load, with eachinjector always in the same cylinder.

Gasoline fuel compositions were subjected to the above-described enginetests whereby the substantial effectiveness of these compositions inminimizing injector deposit formation was conclusively demonstrated. Thefuel used for these tests was a Howell EEE fuel having a T₉₀ (° C.) of160, an olefin content of 1.2% and a sulfur content of 20 ppm. Thedetergent additives used and the percent flow loss for the fuels at tiptemperatures of 173° C. are set forth in Table 3.

TABLE 3 Percent flow loss Sample MMT # (g Mn/gallon) Detergent (ptb)Flow loss (%) 1* None — 10.24 2 1/64 — 5.37 3 1/32 — 6.26 4* NoneMannich¹ (60) 4.33 5 1/64 Mannich¹ (60) 4.16 6 1/32 Mannich¹ (60) 2.91*Comparative Examples ¹The detergent used in Examples 4–6 was acommercially-available Mannich detergent/carrier fluid mixture.

It is clear from examination of Table 3 that the addition of manganesecompounds to fuels for use in direct injection gasoline engines providesunexpected improvements (reductions) in injector deposits when added tothe base fuel as well as improving the effectiveness of a detergent inreducing injector deposits.

It is to be understood that the reactants and components referred to bychemical name anywhere in the specification or claims hereof, whetherreferred to in the singular or plural, are identified as they existprior to coming into contact with another substance referred to bychemical name or chemical type (e.g., base fuel, solvent, etc.). Itmatters not what chemical changes, transformations and/or reactions, ifany, take place in the resulting mixture or solution or reaction mediumas such changes, transformations and/or reactions are the natural resultof bringing the specified reactants and/or components together under theconditions called for pursuant to this disclosure. Thus the reactantsand components are identified as ingredients to be brought togethereither in performing a desired chemical reaction (such as a Mannichcondensation reaction) or in forming a desired composition (such as anadditive concentrate or additized fuel blend). It will also berecognized that the additive components can be added or blended into orwith the base fuels individually per se and/or as components used informing preformed additive combinations and/or sub-combinations.Accordingly, even though the claims hereinafter may refer to substances,components and/or ingredients in the present tense (“comprises”, “is”,etc.), the reference is to the substance, components or ingredient as itexisted at the time just before it was first blended or mixed with oneor more other substances, components and/or ingredients in accordancewith the present disclosure. The fact that the substance, components oringredient may have lost its original identity through a chemicalreaction or transformation during the course of such blending or mixingoperations is thus wholly immaterial for an accurate understanding andappreciation of this disclosure and the claims thereof.

As used herein the term “fuel-soluble” or “gasoline-soluble” means thatthe substance under discussion should be sufficiently soluble at 20° C.in the base fuel selected for use to reach at least the minimumconcentration required to enable the substance to serve its intendedfunction. Preferably, the substance will have a substantially greatersolubility in the base fuel than this. However, the substance need notdissolve in the base fuel in all proportions.

At numerous places throughout this specification, reference has beenmade to a number of U.S. Patents and published foreign patentapplications. All such cited documents are expressly incorporated infull into this disclosure as if fully set forth herein.

This invention is susceptible to considerable variation in its practice.Therefore the foregoing description is not intended to limit, and shouldnot be construed as limiting, the invention to the particularexemplifications presented hereinabove. Rather, what is intended to becovered is as set forth in the ensuing claims and the equivalentsthereof permitted as a matter of law.

1. A method for controlling injector deposits in a direct injectiongasoline engine which comprises introducing into a direct injectionengine with the combustion intake charge a spark-ignition fuelcomposition comprising a) a spark-ignition fuel and b) a fuel-solublecyciopentadienyl manganese tricarbonyl compound.
 2. The method of claim1 wherein the spark-ignition fuel composition comprises the fuel-solublecyclopentadienyl manganese tricarbonyl compound in proportions effectiveto reduce the volume of injector deposits in a direct injection gasolineengine operated on a spark-ignition fuel containing an injectordeposit-controlling amount of said fuel-soluble cyclopentadienylmanganese tricarbonyl compound to below the volume of injector depositsin said direct injection gasoline engine operated in the same manner onthe same spark-ignition fuel except that it is devoid of a fuel-solublecyclopentadienyl manganese tricarbonyl compound.
 3. The method of claim1 wherein the spark-ignition fuel comprises gasoline.
 4. The method ofclaim 1 wherein the spark-ignition fuel comprises a blend ofhydrocarbons of the gasoline boiling range and a fuel-soluble oxygenatedcompound.
 5. The method of claim 1 wherein said cyclopentadienylmanganese tricarbonyl compound comprises at least one member selectedfrom the group consisting of cyclopentadienyl manganese tricarbonyl,methylcyclopentadienyl manganese tricarbonyl and mixtures thereof. 6.The method of claim 1 wherein the fuel-soluble cyclopentadienylmanganese tricarbonyl compound is present in an amount sufficient toprovide 0.0078 to 0.25 gram of manganese per gallon of fuel.
 7. Themethod of claim 6 wherein the fuel-soluble cyclopentadienyl manganesetricarbonyl compound is present in an amount sufficient to provide0.0156 to 0.125 gram of manganese per gallon of fuel.
 8. The method ofclaim 1 wherein the fuel composition further comprises at least oneamine detergent.
 9. The method of claim 8 wherein the amine detergentcomprises at least one member selected from the group consisting ofhydrocarbyl-substituted succinic anhydride derivatives, Mannichcondensation products, hydrocarbyl amines and polyetheramines.
 10. Themethod of claim 9 wherein the hydrocarbyl-substituted succinic anhydridederivatives comprise at least one member selected from the groupconsisting of hydrocarbyl succinimides, hydrocarbyl succinamides,hydrocarbyl succinimide-amides and hydrocarbyl succinimide-esters. 11.The method of claim 1 wherein the fuel composition further comprises acarrier fluid selected from the group consisting of 1) a mineral oil ora blend of mineral oils that have a viscosity index of less than about120, 2) one or more poly-oo-olefin oligomers, (3) one or more poly(oxyalkylene) compounds having an average molecular weight in the rangeof about 500 to about 3,000, 4) one or more polyalkenes, 5) one or morepolyalkyl-substituted hydroxyaromatic compounds and 6) mixtures thereof.12. The method of claim 11 wherein the carrier fluid comprises at leastone poly (oxyalkylene) compound.
 13. The method of claim 1 wherein thefuel composition further comprises at least one additive selected fromthe group consisting of antioxidants, carrier fluids, metaldeactivators, dyes, markers, corrosion inhibitors, biocides, antistaticadditives, drag reducing agents, demulsifiers, dehazers, anti-icingadditives, antiknock additives, anti-valve-seat recession additives,lubricity additives and combustion improvers.
 14. A method for reducingsoot loading in the crankcase lubricating oil of a vehicle having adirect injection gasoline engine which comprises introducing into adirect injection gasoline engine with the combustion intake charge aspark-ignition fuel composition comprising a) a spark-ignition fuel andb) a fuel-soluble cyclopentadienyl manganese tricarbonyl compound. 15.The method of claim 14 wherein the spark-ignition fuel compositioncomprises the fuel-soluble cyclopentadienyl manganese tricarbonylcompound in proportions effective to reduce the amount of soot loadingin the crankcase lubricating oil to below the amount of soot loading insaid crankcase lubricating oil when said vehicle is operated in the samemanner and on the same spark-ignition fuel except that the fuel isdevoid of a fuel-soluble cyclopentadienyl manganese tricarbonylcompound.
 16. The method of claim 14 wherein the spark-ignition fuelcomprises gasoline.
 17. The method of claim 14 wherein thespark-ignition fuel comprises a blend of hydrocarbons of the gasolineboiling range and a fuel-soluble oxygenated compound.
 18. The method ofclaim 14 wherein said cyclopentadienyl manganese tricarbonyl compoundcomprises at least one member selected from the group consisting ofcyclopentadienyl manganese tricarbonyl, methylcyclopentadienyl manganesetricarbonyl and mixtures thereof.
 19. The method of claim 14 wherein thefuel-soluble cyclopentadienyl manganese tricarbonyl compound is presentin an amount sufficient to provide 0.0078 to 0.25 gram of manganese pergallon of fuel.
 20. The method of claim 19 wherein the fuel-solublecyclopentadienyl manganese tricarbonyl compound is present in an amountsufficient to provide 0.0156 to 0.125 gram of manganese per gallon offuel.
 21. The method of claim 14 wherein the fuel composition furthercomprises at least one amine detergent.
 22. The method of claim 21wherein the amine detergent comprises at least one member selected fromthe group consisting of hydrocarbyl-substituted succinic anhydridederivatives, Mannich condensation products, hydrocarbyl amines andpolyetheramines.
 23. The method of claim 22 wherein thehydrocarbyl-substituted succinic anhydride derivatives comprise at leastone member selected from the group consisting of hydrocarbylsuccinimides, hydrocarbyl succinamides, hydrocarbyl succinimide-amidesand hydrocarbyl succinimide-esters.
 24. The method of claim 14 whereinthe fuel composition further comprises a carrier fluid selected from thegroup consisting of 1) a mineral oil or a blend of mineral oils thathave a viscosity index of less than about 120, 2) one or morepoly-a-olefin oligomers, 3) one or more poly (oxyalkylene) compoundshaving an average molecular weight in the range of about 500 to about3000, 4) one or more polyalkenes, 5) one or more polyalkyl-substitutedhydroxyaromatic compounds and 6) mixtures thereof.
 25. The method ofclaim 24 wherein the carrier fluid comprises at least one poly(oxyalkylene) compound.
 26. The method of claim 14 wherein the fuelcomposition further comprises at least one additive selected from thegroup consisting of antioxidants, carrier fluids, metal deactivators,dyes, markers, corrosion inhibitors, biocides, antistatic additives,drag reducing agents, demulsifiers, dehazers, anti-icing additives,antiknock additives, anti-valve-seat recession additives, lubricityadditives and combustion improvers.